Gene scientists claim to have found proof that the Welsh are the "true" Britons.

The research supports the idea that Celtic Britain underwent a form of ethnic cleansing by Anglo-Saxons invaders following the Roman withdrawal in the fifth century.

Genetic tests show clear differences between the Welsh and English

It suggests that between 50% and 100% of the indigenous population of what was to become England was wiped out, with Offa's Dyke acting as a "genetic barrier" protecting those on the Welsh side.

And the upheaval can be traced to this day through genetic differences between the English and the Welsh.

Academics at University College in London comparing a sample of men from the UK with those from an area of the Netherlands where the Anglo-Saxons are thought to have originated found the English subjects had genes that were almost identical.

But there were clear differences between the genetic make-up of Welsh people studied.

The research team studied the Y-chromosome, which is passed almost unchanged from father to son, and looked for certain genetic markers.

Ethnic links: Many races share common bonds

They chose seven market towns mentioned in the Domesday Book of 1086 and studied 313 male volunteers whose paternal grandfather had also lived in the area.

They then compared this with samples from Norway and with Friesland, now a northern province of the Netherlands.

The English and Frisians studied had almost identical genetic make-up but the English and Welsh were very different.

The researchers concluded the most likely explanation for this was a large-scale Anglo-Saxon invasion, which devastated the Celtic population of England, but did not reach Wales.

Dr Mark Thomas, of the Centre for Genetic Anthropology at UCL, said their findings suggested that a migration occurred within the last 2,500 years.

Genetic links

It reinforced the idea that the Welsh were the true indigenous Britons.

In April last year, research for a BBC programme on the Vikings revealed strong genetic links between the Welsh and Irish Celts and the Basques of northern Spain and south France.

It suggested a possible link between the Celts and Basques, dating back tens of thousands of years.

The UCL research into the more recent Anglo-Saxon period suggested a migration on a huge scale.

"It appears England is made up of an ethnic cleansing event from people coming across from the continent after the Romans left," he said.

Celtic Britons

Archaeologists after the Second World War rejected the traditionally held view that an Anglo-Saxon invasion pushed the indigenous Celtic Britons to the fringes of Britain.

Instead, they said the arrival of Anglo-Saxon culture could have come from trade or a small ruling elite.

But the latest research by the UCL team, "using genetics as a history book", appears to support the original view of a large-scale invasion of England.

It suggests that the Welsh border was more of a genetic barrier to the Anglo-Saxon Y chromosome gene flow than the North Sea.

Dr Thomas added: "Our findings completely overturn the modern view of the origins of the English."